1. Field of the Invention
The present invention relates to an error control encoding system in effecting data communication via a fading channel dominated by a burst error in the data communication of a moving body such as an automobile.
2. Description of the Prior Art
Error correcting codes for automatically correcting digital information are essential to improve the reliability of contemporary computer communication systems. Error correcting codes are divided into, depending on correctable error patterns, an error correcting code suited to random errors and an error correcting code suited to burst errors.
In a mobile communication system, a severely degraded transmission path, such as a fading channel, is dominated by a burst error. An interleaving system is a known system used to correct the burst error, and is described in: "Error correcting Codes Entering upon Extensive Use in Various Fields" by Tanaka, Nikkei Electronics, 1975 12-15, p.p. 48 to 52. This employs powerful random error correcting codes for a communication channel dominated by a burst error, interleaves the codes with the digital information, and transforms a burst error to a random error.
However, the interleaving system encounters difficulties with a system having a severe delay time since it takes longer for decoding the data due to the interleaving.
In addition, another error correcting system, known as an automatic repeat request system (ARQ), is described in "Batch Throughput Efficiency of ADCCP/HDLC/SDLC Selective Reject Protocols" by Malcolm C. Easton, IEEE Transactions on Communications, Vol. Com: 28, February, 1980, p.p. 187 to 195.
These systems however needs several hundreds of bits of interleaving for randomizing the signal concerned with the aid of the interleaving since an automobile widely changes its moving speed from zero to a speed of one hundred and several tens of kilometers per hour as well as its receiving level from above minus 100 dBm to about minus several tens of dBm, and results in undesirably long delay times. Thus, a large capacity random access memory (RAM) is required together with a measure for improving the throughput efficiency which has been deteriorated. The deteriorated throughput efficiency is very severe in communication systems using only a burst length error correcting code.